Many embodiments of a cylinder head with a ring-shaped valve or valves has been proposed. Most of them deal with the principle of cylinder charge exchange with a four-stroke or two-stroke cycle with use of the ring-shaped valve. They do not usually deal with construction details of valve sealing. In some cases the seal surfaces of the inner and outer valve seats are on one planar or conical surface in order to be able to easily precisely machine these surfaces in one operation and ensure sufficient tightness of the ring-shaped valve. These solutions are described e.g. in U.S. Pat. No. 2,222,730, U.S. Pat. No. 2,222,731, DE 3438847 A1, or U.S. Pat. No. 5,673,656. Tightness of the ring-shaped valve in both valve seats is however a problem not only from the point of view of precise machining of valve seats and valves, but even with respect to thermal and mechanical deformations. This could be deformations of the cylinder head, of both of the valve seats, and finally of the ring-shaped valve. A further problem for tightness of the ring-shaped valve is unequal wear of seat faces of the outer and inner seat and valve. The question is the design of seats and cylinder head with respect to their installation into the cylinder head, adjustment and repairs.